What is a family preference category? Qualified relatives of a U.S. citizen or permanent resident who are not known as an immediate relative may have to wait for a visa to become available before they can apply for permanent residency. These categories are known as Preference Categories and include:
Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. This sediment can include minerals, small pieces of plants and other organic matter. The sediment is compressed over a long period of time before consolidating into solid layers of rock. Sedimentary rocks forms layers called strata which can often be seen in exposed cliffs.
The most common clastic sedimentary rocks are breccia and conglomerate (formed from gravel), sandstone (from sand), siltstone (from silt), and shale (from clay). B. CHEMICAL SEDIMENTARY ROCKS. Chemical sedimentary rocks are crystalline, that is made of crystals interlocked with each other.ediment is a general term that indicates loose grains (such as the sand at the beach) and chemical precipitates (such as crystals of salt). Sedimentary rocks can be subdivided in three categories: clastic, chemical, and biochemical sedimentary rocks.